Question

Find the average speed of image forming when the convex lens has a focal length of 20m and the object is placed at 60 metre. speed of object moving is 20ms​

Answer 1

From lens equation

v

1

−

u

1

=

f

1

v

1

−

(−20)

1

=

(.3)

1

=

3

10

v

1

=

3

10

−

20

1

v

1

=

60

197

;v=

197

60

Velocity of image wrt. to lens is given by v

I/L

=m

2

v

O

/L

direction of velocity of image is same as that

of object

v

O/L

=5m/s

v

I/L

=(

197×20

60×1

)

2

(5)

1.16×10

−3

m/s towards the lens

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